Strategies in the preparation of conductive polyvinyl alcohol hydrogels for applications in flexible strain sensors, flexible supercapacitors, and triboelectric nanogenerator sensors: an overview

Elastic conductors play a crucial role in the fabrication of wearable electronic devices and human–computer interaction devices. Among the various candidates for elastic conductors, hydrogels, featuring 3-D swollen macromolecular networks, exhibit exceptional stretchability and biocompatibility. Notably, physical hydrogels based on poly (vinyl alcohol) (PVA), which contains a substantial number of reactive groups (-OH groups), stand out due to their remarkable biocompatibility, superior mechanical properties, and chemical stability. This review focuses on recent advancements in the composite strategy, preparation, and current applications of PVA-based conductive composite hydrogels. Firstly, PVA-based conductive hydrogels are classified based on various conductive treatments: (i) introduction of conductive fillers to the PVA with a single network structure; (ii) introduction of conductive fillers to the PVA with double/multiple network structures (e.g., PVA/carboxymethylcellulose, PVA/poly(acrylamide)); (iii) creation of double-network PVA hydrogel combined with conductive polymers including poly(3,4-ethylene-dioxythiophene)/poly(styrenesulfonate), poly(aniline), poly(pyrrole); (iv) addition of ions to a pure PVA network; (v) addition of ions to the PVA with double network structures (e.g., PVA/sodium alginate, PVA/hydroxyethylcellulose). This review includes a comparative analysis of different conductive hydrogel systems. Secondly, PVA-based conductive hydrogels with diverse functions, such as strain sensing, shape memory, antifreeze properties, transparency, and pH response, are thoroughly reviewed. Thirdly, the latest advancements in the applications of PVA-based conductive hydrogels are demonstrated, including flexible super-capacitors, human–computer interaction devices, and triboelectric nanogenerator sensors. Finally, a summary of the current state of development and critical issues with PVA conductive hydrogels is provided, along with an outlook on how to address each.

Graphical Abstract

Systematic review on PVA conductive hydrogels: outlines preparation strategies and applications in flexible electronic devices.